The concept of using explosive energy to deform a metal plate into a coherent penetrator while simultaneously accelerating it to extremely high velocities offers a unique method of employing a kinetic energy penetrator without the use of a large gun. A typical explosively formed projectile (EFP) is comprised of a metallic liner, a case, an explosive section, and an initiation train. Very often there is also a retaining ring to position and hold the liner-explosive subassembly in place. EFP warheads are normally designed to produce a single massive, high velocity penetrator. After detonation, the explosive products create enormous pressures that accelerate the liner while simultaneously reshaping it into a rod or some other desired shape. The EFP then hits the target at a high speed, delivering a significantly high mechanical power.
Two major applications have evolved for explosively formed projectiles or warheads, namely, long-standoff sensor-fuzed submunitions and medium-standoff, close-overflight missiles. The former application, which is the more traditional one, requires the formation of a single-piece EFP capable of flying in a stable fashion to the target. This refinement has led to the flared EFP rod and, more recently, to the finned EFP rod designs.
For the medium or short-standoff applications, a new type of EFP was developed. The need for an aerodynamic shape is not necessary for these applications because of the short distance the EFP must travel, hence, the length of the rod was increased and the flared tail was eliminated from the design. In fact, some of these rods are purposely stretched beyond their breaking point and fracture into several pieces resulting in greater total length.
An EFP warhead configuration may be comprised of a steel case, a high-explosive charge, and a metallic liner. Explosively formed penetrator (EFP) warheads have been designed to project a single massive high velocity penetrator to attack the top of armored vehicles. Such armor perforation capability needs further improvement to counter new generations of harder armored vehicles, without resorting to a larger caliber weapon system. In developing a warhead configuration that meets system constraints and also meets performance requirements, several parameters in the warhead configuration must be redesigned to achieve an optimum configuration. Several warhead configurations have been developed to accommodate varying system constraints.